The Archaeology of Food and Cooking

Residues of the Past: Archaeological Investigations of Diet

I’m afraid the fall season made me a bit… nuts. All of this going on about acorns in my previous blog, and I haven’t even told you how we know that residents of the Cloudman site were acorn-eaters. Or how we know what people in the past were eating at all!

There are three general types of food remains: macroremains, microremains, and chemical food signatures. All require brilliant specialized archaeologists who are trained to identify each specific type.

Carbonized seeds found at archaeological sites in Scotland (image source)

Macroremains are visible to the eye and include faunal remains, or animal bones, and floral remains, such as seeds and nutshells (although both paleoethnobotanists and zooarchaeologists may use a microscope to examine specimens more closely for more accurate identification).

Happy little maize starch (photo by Rebecca Albert)

Microremains are only visible via microscope. These include phytoliths and starches. Phytoliths are small silica structures that fill the spaces between plant cells, and these spaces are unique to different species. Starches are small structures found in all plants, but they are most abundant in seeds and tubers.

Chemical food signatures are a fascinating field of study that is ever improving and expanding. Lipid residue analyses analyzes the fatty acids of plants and animals left behind in tools used to process and cook food, such as ceramic cooking vessels.

Stable isotope analysis can be used to understand the origins of dietary elements. Most often, this is applied to human skeletal remains, allowing us insight directly to an individual’s diet. However, some researchers (myself included) have begun using stable isotope values of food residues in order to evaluate the nature of the foods represented by those residues.

Nitrogen isotope ratios indicate a terrestrial vs. aquatic diet, while ratios of different carbon isotopes can show whether past diet consisted of temperate-climate plants or tropical plants. This is important in the United States and Canada, where most plants are temperate. If the carbon isotope ratios look more like those of tropical plants, we know it’s usually an indicator of the most famous and widespread tropical plant to enter this area : maize (corn), which was domesticated from a tropical grass in Mexico!

A new type of chemical analysis involves using proteins in food residues to identify food content, as in this incredible study from the site of Catal Hoyuk in Turkey (LINK). I’m excited to learn more about this method!

Plant and animal macroremains are by far the most common evidence of past diet used by archaeologists, and, as you can imagine, they are extremely useful. However, bones and seeds are organic, meaning that they break down and degrade over time. In areas such as the Upper Great Lakes, preservation of organic remains is poor because of the effect of frost/thaw on such materials is very damaging, and because the soils tend to be quite acidic.

One of the reasons I chose to focus on food residues adhered to pottery from the Cloudman site (besides the fact that I am hot for pots) is that it provides direct evidence of foods cooked in the pottery vessel. Carbonization (aka burning) actually helps preserve organic remains, such as starches. Phytoliths, made of silica, are inorganic, so they preserve beautifully. Lipid residues are actually absorbed into the walls of cooking vessels, which serves to preserve them for later study.

This is the most exciting image I could find for lipids. Sorry. (image source)

At the Cloudman site, the many of the pots (71% of those tested) contained the lipid residues of nuts (1). Of the precious macroremains we have from the site, acorns are the most abundant nut encountered (2). There is also a high likelihood that a convenient oak stand was located not far from the site during the precontact era (3). Ethnographic records show that acorns were the most common nut consumed by the historic era Ojibwe, who at the time inhabited much of the northern Great Lakes (4, 5). Based on this information, I believe that the nut lipids in the pottery were mostly the result of processing acorns, and that these were important to the indigenous residents of the Cloudman site throughout history.

As you can see from the descriptions above and from my acorn case study, every type of food remain is important and tells about a unique aspect of past diet and cuisine. They are informative on their own and stronger together.